Detailed project information

During the past decade, much progress has been made in understanding the major abiotic factors that simultaneously control the growth of oceanic phytoplankton. The intensity of visible light is the primary factor regulating growth. Furthermore, growth is controlled by major nutrients such as nitrate or trace nutrients such as iron (Fe). On top of this, ultraviolet radiation (UVR: 280-400 nm) strongly diminishes marine phytoplankton growth in situ. Knowing this, there is the need to understand how the various regulating factors interact, but in particular, how they augment each other.

UVR stress in marine phytoplankton can be coupled to damage to photosystems, membranes or macromolecules such as enzymes or DNA. Indirect intracellular damage may be brought about by the action of Reactive Oxygen Species (ROS), which cause oxidative stress. Oxidative stress is a common phenomenon in a broad range of organisms. Yet, very little is known about the occurrence and consequences of oxidative stress in marine microalgae. One effect could be the induction of oxidative DNA damage (DNA strand breaks, 8-oxoG), which may eventually cause mutation or cell death. Nothing is known about the in situ occurrence of these lesions in marine phytoplankton.

The UVR vulnerability of phytoplankton is thought to be related with the capacity of organisms to exploit UVR defense mechanisms such as the synthesis of UVR screening substances, repair enzymes or so-called antioxidants. Consequently, unfavorable environmental conditions such as the occurrence of (trace)nutrient depletion may interfere with UV vulnerability because defense systems require energy and nutrients for adequate functioning. Still, these theoretical considerations have hardly resulted in more integrative studies, for example focusing on the interaction between trace nutrient availability and UV exposure in situ.

The proposed project is set up to untangle regulating effects of trace nutrients on defense mechanisms of oceanic phytoplankton against harmful ultraviolet radiation. Particular attention will be given to the activity of antioxidant enzymes, which have a structural requirement for trace nutrients.